Bosch SMS44 very slow to fill

[sharpener]

We have a Bosch SMS4452GB/14 which is very slow to fill. The noise it makes during filling sounds as though the water is being squirted through a small aperture. Sometimes the timer does not advance when the fill is complete and requires nudging, this used to be only on the first (cold rinse) part of the cycle but now happens on all the fill phases.

I have taken out the fill valve and stripped it down, all the orifices are clear (including the tiny pilot ports) and it works OK. Is there somewhere else which is prone to blockage? Does this account for the failure of the timer to advance, or is this a separate fault?

Many thanks, Chris

[electrofix]

when you say the valve works ok how did you test it

one small split in a diaphragm and the valve will slow fill or stop

Dave

https://shop.ukwhitegoods.co.uk/091051-dishwasher-water-inlet-valve

[sharpener]

Thanks for yr prompt reply Dave.

I set up a test rig on the kitchen worktop, with valve connected to water supply and waste, mains to solenoid. (I am an electrical engineer by profession so am used to this kind of setup.)

Flow rate seemed OK after I had cleared the 3 pilot holes in the diaphragm (though there was no obvious blockage). IIRC these holes are smaller than the strainer in the supply pipe so it is possible they can have got blocked by debris the water supply, but perhaps you can say if there is another likely cause as it’s a lot of work to dismantle it all again and it didn’t really fix the problem anyway.

Thanks, Chris

[electrofix]

the valve has 2 sections
the valve itself + the safety shutoff diaphragm. if the valve is energised and the unit has not tripped the safety diaphragm then its faulty.

try running the unit without the hose connected to the safety valve. it should then function normally if yes suspect the overflow section if no then its the valve

you can take out the valve diaphragm and look for holes in the folds. if water can get behind the diaphragm faster than it leaves it the valve wont open fully

Dave

[sharpener]

Thanks Dave, I had forgotten about the safety shut off function but it was working OK when tested so I don’t think it is that,

I will take the valve apart again when we are not needing to use the dishwasher so much.

Even when it has succeeded in filling, the controller does not advance to start the wash or rinse cycle and has to be nudged. I am thinking perhaps there a pressure or level switch which determines when it moves on from the fill phase and is that is also faulty. Any thoughts on this?

TIA and happy new year, Chris

[electrofix]

on this model the water fills by loading the side and flowing into the unit over a float unit. this unit activates the motor in the timer so it can move forward. if you trip this switch manually you can see if it moves on then. don’t do it with no water in case heater energises

Dave

[Author]

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